1. Field of the Invention
The present invention relates to an automotive display apparatus, and more particularly to, an automotive display apparatus in which display light from a displayer passes through a transmissive first reflector plate and is reflected on a second reflector plate toward the first reflector plate. Then, the light reflected on the second reflector plate is further reflected on the first reflector-plate toward an eye range, thereby a display image of the displayer is recognized from the eye range as a virtual image within a displaying range of the first reflector plate through a face plate which is disposed between the first reflector plate and the eye range.
2. Description of the Prior Art
A conventional automotive display apparatus described above is shown in FIG. 4, in which a display image of a displayer is indicated as far as possible without making the apparatus larger. In the figure, denoted 11 is a dashboard, in which a light emitting displayer 12 such as a liquid crystal displayer and a fluorescent display tube is installed to display information on driving condition such as a vehicle speed. A transmissive reflector plate 13 is disposed on a display surface side of the displayer 12 to allow the display light from the displayer 12 to pass therethrough. At a position opposing the displayer 12 with the reflector plate 13 in between, a flat or concave mirror 14 is installed so as to form a predetermined offset angle .theta. between incident and reflected lights.
When the offset angle is 0.degree. and a driver recognizes the display image from the eye range 21 as illustrated in FIG. 5, the driver recognizes an image with a background in which a portion adjacent to a face of the driver is enlarged. Then, when the driver's face is exposed to an external light under such conditions, the contrast of the image is to be reduced, which diminishes a commercial value of the apparatus. To prevent the above phenomenon, the prescribed offset angle .theta. is provided as shown in FIG. 6, an optical axis of the light reflected on the mirror 14 is absorbed on an inner face of a meter hood 11a to prevent the image of the driver on the mirror 14 from being observed from the eye range 21.
Further, a concave face plate 15 is disposed at a front portion of the dashboard 11 to protect the reflector plate 13 and the mirror 14 and to keep them free from dust, the reflector plate 13 and the mirror 14 otherwise tending to collect dust to deteriorate the quality and recognizability of the image displayed. The face plate 15 may be made of a dark color transparent smoked acrylic resin or the like.
A similar problem arises to the face plate also like the mirror 14, therefore, an upper end of the face plate 15 is inclined on a side opposite to the driver and a center 01 of the concave face is positioned at an upper portion on the drive's side as illustrated in FIG. 7. A reference symbol F is a focus. As described above, the face plate 15 is inclined so that the optical axis of the light reflected by the face plate 15 is absorbed on the inner face of the meter hood 11a, which prevents the image of the driver on the face plate 15 from being recognized from the eye range 21. As clearly understood by comparing FIGS. 8A and 8B to each other, the space in the dashboard (slant line portions in the figure) of the apparatus of which upper end is inclined on the opposite side to the driver, which is shown in FIG. 8A, is smaller than that of the apparatus of which upper end is inclined on the side of the driver in FIG. 8B.
In the structure described above, the display light of the display image is emanated from the displayer and passes through the reflector plate 13 to be reflected on the mirror 14. The thus totally reflected light is further reflected on the reflector plate 13 toward the eye range 21 on the side of the driver, from which the driver recognizes the image.
Therefore, when the reflector plate 13 is observed from the eye range 21, the display image is recognized as a virtual image X in a viewing area A behind the reflector plate 13. The viewing area A is defined in the figure by a first line that passes through the upper end 21U of the eye range 21 and the lower end of the mirror 14a reflected on the reflector plate 13 and a second line that passes through the lower end 21D of the eye range 21 and the upper end of the mirror 14a reflected on the reflector plate 13.
The virtual image X recognized as described above is formed within the range of the mirror 14a reflected in the reflector plate 13 and at a position remote by a distance corresponding to the overall length of the light path, which provides a good remote displaying effect.
With the structure described above, the optical axis of the light reflected on the mirror 14 and the face plate 15 are absorbed on the inner face of the meter hood 11a. However, the directions of the light reflected by the mirror 14 and the center 01 of the face plate 15 approach each other. As a result, the display image X is reflected on a back face of the face plate 15 to form a ghost-causing virtual image X1 as illustrated in FIG. 7 and the image X1 enters the viewing range A1 of the mirror 14a which is reflected on the reflector plate 13 shown in FIG. 6, which allows the image X1 to be recognized from the eye range 21 as a ghost.
When the ghost is observed by the driver, the display image X and the ghost X1 overlap each other, which reduces the contrast of the display image to reduce the recognizability of the display image. Further, the ghost as an unstable image will make the driver irritated, which reduces a commercial value of the apparatus.
An alternative countermeasure is to apply AR coating (non-reflective coating) to a part of the face plate 15 on which the display image X is reflected to reduce the reflected light. However, the countermeasure is costly.